Problem: Express your answer as a mixed number simplified to lowest terms. $15\dfrac{5}{8}-3\dfrac{2}{5} = {?}$
Separate the whole numbers from the fractional parts: $= {15} + {\dfrac{5}{8}} - {3} - {\dfrac{2}{5}}$ Bring the whole numbers together and the fractions together: $= {15} - {3} + {\dfrac{5}{8}} - {\dfrac{2}{5}}$ Subtract the whole numbers: $=12 + {\dfrac{5}{8}} - {\dfrac{2}{5}}$ Find a common denominator for the fractions: $= 12+\dfrac{25}{40}-\dfrac{16}{40}$ Subtract the fractions: $= 12+\dfrac{9}{40}$ Combine the whole and fractional parts into a mixed number: $= 12\dfrac{9}{40}$